Preparing for Installation 2-21
Site Wiring Guidelines
Synchronous Optical Network Connection Guidelines
The Synchronous Optical Network (SONET) specification for fiber-optic transmission
defines two types of fiber:
•Single mode
•Multimode
Data transmission in either mode occurs by means of bundles of light rays that enter the
fiber at a particular angle.
Single-mode fiber allows only one mode of light to propagate through the fiber; multimode
fiber allows multiple modes of light to propagate through the fiber.
Multiple modes of light propagating through the fiber travel dif ferent dist ances, dependin g
on entry angles, causing the light to arrive at destinations at different times. This
phenomenon is called modal dispersion.
Single-mode fiber provides higher-bandwidth transmission and supports greater cable
distances than multimode fiber. Table2-3 lists the maximum distances for single-mode and
multimode fiber-optic transmissions, as defined by SONET.
If the distance between two connected stations is greater than the maximum distance
specified in Table2-3, significant signal loss can result, making fiber-optic transmission
unreliable.
Table2-3 SONET Maximum Fiber-Optic Transmission Distances
Transceiver Type Maximum Distance between Stations1
1. Typical results; you should use the power budget calculations to determine the
actual distances.
Single-mode Up to 9 miles (14.5 km)
Multimode Up to 1.5 miles (2.4 km)